algorithm to compute waiting time for FCFS scheduling in python

Question

Consider the following code that takes input processes and their arrival times and sort them according to FCFS algorithm, so i\'ve been thinking about algorithms to compute avg

Answer 1

Concept: https://www.geeksforgeeks.org/program-fcfs-scheduling-set-2-processes-different-arrival-time/

processes = [
    {"pid": "P0", "burst_time": 5, "arrival_time": 0, "service_time": None, "waiting_time": None},
    {"pid": "P1", "burst_time": 3, "arrival_time": 1, "service_time": None, "waiting_time": None},
    {"pid": "P2", "burst_time": 8, "arrival_time": 2, "service_time": None, "waiting_time": None},
    {"pid": "P3", "burst_time": 6, "arrival_time": 3, "service_time": None, "waiting_time": None}
]

# No waiting time for first process
processes[0]["waiting_time"] = 0
# Service_time of the first process is it's arrival time
processes[0]["service_time"] = processes[0]["arrival_time"]

for i in range(1, len(processes)):
    # Case where process comes when processor is in idle state
    if processes[i]["arrival_time"] > (processes[i - 1]["service_time"] + processes[i - 1]["burst_time"]):
        processes[i]["service_time"] = processes[i]["arrival_time"]
    else:
        processes[i]["service_time"] = processes[i - 1]["service_time"] + processes[i - 1]["burst_time"]

    processes[i]["waiting_time"] = processes[i]["service_time"] - processes[i]["arrival_time"]

total_waiting_time = 0

for process in processes:
    total_waiting_time += process["waiting_time"]

avg_waiting_time = total_waiting_time / len(processes)

print("Average Waiting Time:", avg_waiting_time)